Low temperature and cryogenic refrigeration is typically used to cool fluid streams for cryogenic separations, trap water vapor to produce low vapor pressures in vacuum processes and to cool articles in manufacturing processes, such as semiconductor wafer processing, cooling of imaging detectors and radiation detectors, industrial heat transfer and biopharmaceutical and biomedical applications and biomedical storage, and chemical processing. A refrigeration cycle, generally, compresses a refrigerant gas, condenses the gas through an exchange of heat with a coolant and may further exchange heat with returning decompressed or expanded gas to achieve additional cooling. Often, portions of the refrigeration cycle have two-phase liquid/gas flow.
A typical refrigeration cycle may have one or more heat exchangers. These heat exchangers may act to condense compressed gas, absorb heat after expansion, or exchange heat between compressed fluid and returning expanded gas. Typical applications use shell and tube, tube in tube, or twisted tube heat exchange systems. Others use plate type heat exchangers.
Shell and tube, tube in tube, or twisted tube heat exchangers are inexpensive and exhibit low pressure drop, even in two-phase flow environments. However, tubular exchangers have a low surface area per unit volume or length of the exchanger. To achieve a desired heat transfer surface area, long extensions of tubing are used. In confined spaces, these heat exchangers are wrapped and contorted, increasing cost.
Plate type heat exchangers have a better surface area to volume ratio and are more compact. However, typical plate type heat exchangers are more expensive and are not efficient in two-phase flow environments, often exhibiting poor distribution of each phase between channels. Poor distribution leads to reduced stability, reduced heat exchanger effectiveness, reduced heat transfer coefficients, reduced system efficiency, increased pressure drop, and, in the case of ultra low and cryogenic temperature applications, can lead to freeze out conditions. On the other hand, typical two-phase flow distributors used in plate-type heat exchangers have a high pressure drop (greater than about 18 psi).
As such, an improved heat exchanger would be desirable.